Part human, part robot, these beings are bonafied cyborgs. They're referred to as axioms instead of cyborgs as the word "cyborg" is considered a slur. Additionally, considering that Neurodonors are also part human part robot, the use of the word "cyborg" can be confusing. The term "axiom" specifically refers to someone who is more human than robot, or still appears mostly human. Neurodonors are usually markedly animalistic.
COG regulations on axiom parts prohibit the sale or usage of any parts that would supercede normal human capablities; despite this, axioms still face a great deal of fear from their human colleagues.
The human brain can only run four limbs; and as such, all robots (even Neurodonors) must have at most four legs.